Selective gas etching for self-aligned pattern transfer

ABSTRACT

Selective gas etching for self-aligned pattern transfer uses a first block and a separate second block formed in a sacrificial layer to transfer critical dimensions to a desired final layer using a selective gas etching process. The first block is a first hardmask material that can be plasma etched using a first gas, and the second block is a second hardmask material that can be plasma etched using a second gas separate from the first gas. The first hardmask material is not plasma etched using the second gas, and the second hardmask material is not plasma etched using the first gas.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 15/284,862, filed Oct. 4, 2016, the entire disclosure of whichis incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to semiconductor fabrication and inparticular to semiconductor fabrication in the 7 nm node and beyond.

BACKGROUND OF THE INVENTION

Semiconductor fabrication involves the creation of the desired patterninto a layer or layers of material. Creation of the desired pattern intoa specific layer involves a pattern transfer process that utilizes masksin combination with conventional etching processes such as opticallithography and sidewall image transfer (SIT). The need for the creationof desired patterns having pitches of 26 nm or less and nodes of 10 nmor less including both two-dimensional and three-dimensional patternsexposes the limitations of conventional methods for image creation andtransfer. For example, a block cut is needed for both mandrel andnon-mandrel metals wires. However, block pattern overlay is a continuingproblem as the pattern pitch decreases. Existing block masks will cutwires that do not need to be cut. In addition, tall spacers cause pitchwalking, and existing processes can damage spacers and mandrelmaterials. Therefore, a semiconductor fabrication process is desiredthat compensates for the limitation of a 40 nm pillar size, overlayshift and critical dimension uniformity.

SUMMARY OF THE INVENTION

Exemplary embodiments are directed to systems and methods for creatingand transforming patterns in semiconductor fabrication where the patternhas a small pitch, e.g., 26 nm, and is a 10 nm node, a 7 nm node or a 5nm node. A selective, i.e., a chemistry selective gas etching process isutilized that provides for self-aligned transfer of the desired patternsand critical dimensions to the appropriate semiconductor layer. Thematerials of the different layers and masks are chosen so that theselayers and masks are selectively etched using a gas etching process byvarying the chemistry of the gas etching process. To achieve the desiredpitch, two block masks are used, a first bock mask and a second blockmask. Each block mask is formed from a different hardmask material. Thehardmask material of each block facilitates the selective etching.

Each block mask is positioned to mask and to cut the desired portions ofthe semiconductor layer. In one embodiment, the first block mask isarranged to cut mandrel wire, and the second block mask is arranged tocut non-mandrel wire. The first and second block masks are preferablyformed on a common layer. In one embodiment, a sidewall image process(SIT) is utilized after the first and second block masks are formed. TheSIT process applies an arrangement of mandrels and spacers over thelayer containing the first and second block masks. The mandrels andspaces are aligned such that the first block mask is located below amandrel and has a dimension extending perpendicular to the mandrels thatis at least as big at the width of the mandrel and the spacer on eitherside of the mandrel. In addition, the second block mask is located belowa space between adjacent mandrels and has a dimension extendingperpendicular to the mandrels that is at least as big at the width ofthe space between the mandrels and the spacers on either side of thespace. Selective gas etching during the SIT process is then used totransfer the mandrel and spacer dimension to the first block mask andthe space and spacer dimensions to the second block mask. These firstand second block masks are then used to transfer these dimensions tolower layers. Therefore, smaller dimensions can be transferred orprinted on the desired layers using a gas etching process that overcomesthe limitations of physical printing and etching processes.

Exemplary embodiments are directed to a method for selective gas etchingfor self-aligned pattern transfer. A first block is formed in asacrificial layer. The first block is made of a first hardmask materialthat can be plasma etched using a first gas. A second block separatefrom the first block is also formed in the sacrificial layer. The secondblock is formed of a second hardmask material that can be plasma etchedusing a second gas separate from the first gas. The first and secondhardmask materials are selected such that the first hardmask material isnot plasma etched using the second gas, and the second hardmask materialis not plasma etched using the first gas. In one embodiment, the firstblock and the second block have dimensions along the sacrificial layer,e.g., in two dimensions, greater than or equal to critical dimensions tobe transferred to layers below the sacrificial layer. In one embodiment,the first hardmask material and the second hardmask material compriseinorganic hardmask materials. For example, the first hardmask materialis titanium nitride, and the second hardmask material is siliconnitride.

In one embodiment of forming the first block, the first hardmaskmaterial is deposited across the sacrificial layer, and a firstphotoresist stack having a silicon containing anti-reflective coatingand an organic planarization layer is formed on the first hardmaskmaterial. The first photoresist stack has a size and locationcorresponding to the first block. Reactive ion etching with carbontetrafluoride is used to remove the silicon containing anti-reflectivecoating. Then, reactive ion etching with chlorine gas is used to etchthe first hardmask material. Plasma etching is used to remove theorganic planarization layer, leaving only the first block in thesacrificial layer.

In one embodiment, forming the second block includes depositing thesecond hardmask material across the sacrificial layer and over the firstblock. The second hardmask material thickness is adjusted to equal afirst block thickness, and a second photoresist stack having a siliconcontaining anti-reflective coating and an organic planarization layer isformed on the second hardmask material. The second photoresist stack hasa size and location corresponding to the second block. Reactive ionetching with fluoromethane is used to remove the silicon containinganti-reflective coating and to etch the second hardmask material, andplasma etching is used to remove the organic planarization layer,leaving only the second block and the first block in the sacrificiallayer. The resulting sacrificial layer containing the first block andthe second block is used in sidewall image transfer to transfer adesired pattern into layers below the sacrificial layer. In oneembodiment, using the sacrificial layer comprising the first block andthe second block in sidewall image transfer further includes using thefirst block to transfer a mandrel critical dimension to layers below thesacrificial layer and using the second block to transfer a non-mandrelcritical dimension to the layers below the sacrificial layer.

In one embodiment, a titanium containing anti-reflective coating isdeposited across the sacrificial layer and over the first block andsecond block. A titanium containing anti-reflective coating thickness isadjusted to equal a first block thickness and a second block thickness.A plurality of amorphous silicon mandrels are formed on the sacrificiallayer such that one amorphous silicon mandrel is located above the firstblock and one space between adjacent amorphous silicon mandrels islocated above the second block. In order to form the plurality ofamorphous silicon mandrels on the sacrificial layer, an amorphoussilicon layer is deposited on the sacrificial layer, and an organicplanarization layer is deposited on the amorphous silicon layer. Asilicon containing anti-reflective coating layer is deposited on theorganic planarization layer, and a plurality of resist mandrels isformed on the silicon containing anti-reflective coating layer. Theamorphous silicon layer is etched to form the plurality of amorphoussilicon mandrels corresponding to the plurality of resist mandrels.

In one embodiment, an oxide spacer is deposited over the plurality ofamorphous silicon mandrels and the sacrificial layer, and anisotropicetching is use to remove the oxide spacer from a top of each amorphoussilicon spacer and from the space between adjacent amorphous siliconmandrels, leaving an oxide spacer on either side or each amorphoussilicon mandrel. In one embodiment, the first block extends completelyunder one of the amorphous silicon mandrels and the oxide spacers oneither side of one of the amorphous silicon mandrels, and the secondblock extends completely under the one space between adjacent amorphoussilicon mandrels and oxide spacers located on either side of the onespace between adjacent amorphous silicon spacers. The first gas and thesecond gas are used in reactive ion etching to transfer a first criticaldimension defined by one of the amorphous silicon mandrels and the oxidespaces on either side of one of the amorphous silicon mandrels to thefirst block and to transfer a second critical dimension defined by theone space between adjacent amorphous silicon mandrels and oxide spacerslocated on either side of the one space between adjacent amorphoussilicon mandrels to the second block.

In one embodiment, reactive ion etching with the first gas is used totransfer the first critical dimension to the first block, to transferthe first critical dimension into the titanium containinganti-reflective coating layer located under amorphous silicon mandrelsand the oxide spaces on either side of the amorphous silicon mandrelsand to remove the first block and titanium containing anti-reflectivecoating layer located in spaces between oxide spacers located on eitherside of spaces between adjacent amorphous silicon mandrels. In addition,reactive ion etching with the second gas is used to transfer the secondcritical dimension to the second block and to transfer a spacer widthfor each oxide spacer to the titanium containing anti-reflective coatinglayer. In one embodiment, the first gas is chlorine gas, and the secondgas is carbon tetraflouride gas.

In one embodiment, all spaces between oxide spacers located on eitherside of spaces between adjacent amorphous silicon mandrels are filledwith a backfill organic planarization layer following reactive ionetching with the first gas. Reactive ion etching with hydrogen bromideis then used to remove the amorphous silicon mandrels before reactiveion etching with the second gas. Plasma etching removes the backfillorganic planarization layer, and oxide reactive ion etching is used toremove the plurality of oxide spacers and to etch a final pattern intoan oxide layer below the sacrificial layer. The final pattern is definedby the second block, the first block and the spacers widths in thetitanium containing anti-reflective coating layer corresponding to eachoxide spacer in the plurality of oxide spacers in the sacrificial layer.In one embodiment, reactive ion etching with ion gas is used to etch thefinal pattern into a final layer below the oxide layer and to remove thesacrificial layer. In one embodiment, the final layer is titaniumnitride.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of a sacrificial layer of titaniumnitride over lower layers with a photoresist mask over a portion of thetitanium nitride; and

FIG. 2 is a schematic representation of the titanium nitride etched toform a first block in the sacrificial layer;

FIG. 3 is a schematic representation of the sacrificial layer beingfilled and the first block being covered by a layer of silicon nitride;

FIG. 4 is a schematic representation of the silicon nitride in thesacrificial layer etched to a thickness equal to the first block;

FIG. 5 is a schematic representation of a photoresist mask over aportion of the silicon nitride in the sacrificial layer;

FIG. 6 is a schematic representation of the silicon nitride etched tothe second block and an OPL on top of the second block;

FIG. 7 is a schematic representation of the OPL removed, leaving onlythe first block and the second block in the sacrificial layer;

FIG. 8 is a schematic representation of the sacrificial layer beingfilled and the first and second blocks being covered by a filler layerof titanium containing anti-reflective coating;

FIG. 9 is a schematic representation of the SiARC in the sacrificiallayer adjusted to a thickness equal to the first and second blocks;

FIG. 10 is a schematic representation of a plurality of resist mandrelsformed over the sacrificial layer;

FIG. 11 is a schematic representation of the pattern of the resistmandrels transferred to an amorphous silicon layer on top of thesacrificial layer;

FIG. 12 is a schematic representation of an oxide spacer formed over theamorphous silicon mandrels and the sacrificial layer;

FIG. 13 is a schematic representation of the oxide spacer removed fromthe top of the mandrels and the spaces between mandrels;

FIG. 14 is a schematic representation of a mandrel critical dimensionformed in the first block;

FIG. 15 is a schematic representation of an OPL backfill added to fillthe etched portions;

FIG. 16 is a schematic representation of the removal of the amorphoussilicon mandrels;

FIG. 17 is a schematic representation of the etching of the non-mandrelcritical dimension into the second block and the etching of the spacersinto the TiARC;

FIG. 18 is a schematic representation of the removal of the OPL;

FIG. 19 is a schematic representation of the etching of the mandrelcritical dimension, non-mandrel critical dimension, spacer dimensionsinto the oxide layer with oxide spacer removal;

FIG. 20 is a schematic representation of the etching of the mandrelcritical dimension, non-mandrel critical dimension, spacer dimensionsinto the final layer; and

FIG. 21 is a flow chart illustrating an embodiment of a method forselective gas etching for self-aligned pattern transfer.

DETAILED DESCRIPTION

Exemplary embodiments provide for the manufacture of semiconductordevices having a pitch of 26 nm or less. These semiconductor devicesinclude 10 nm node, 7 nm node and 5 nm node devices. An etching processthat can utilize different gases is used in the transfer the desiredpattern to the desired layer in the semiconductor. Changing the gas usedin the etching process changes the materials that will be etched by theetching process. Therefore, the materials used in the blocks, masks andsacrificial layers to transfer the desired pattern to the desired layerare chosen based upon an ability to be selectively etched throughvarying the chemistry, i.e., the gas, in the etching process. Inaddition, the etching process allows for the transfer of smallercritical dimensions.

Exemplary embodiments are directed to the semiconductor product madeaccording to the methods of the present invention. In addition,exemplary embodiments are directed to a semiconductor product having theimproved tolerances in a 10 nm or 7 nm node for semiconductor patternswith a pitch of less than about 26 nm. In general, formation of thesemiconductor product is a multi-layer process in which layers ofdifferent materials are deposited and etch in order to transfer apattern to a given final layer of material. Multiple final layers can beetched to achieve the desired two-dimensional and three-dimensionalpatterns in the overall semiconductor product.

Referring initially to FIG. 1, a final layer 100 of material is formedor deposited on a support 102. Suitable materials for the final layerinclude, but are not limited to, titanium nitride (TiN) and silicon. Thefinal layer can be formed or deposited using any known and availablemethod including, but not limited to, chemical vapor deposition andphysical vapor deposition. An oxide layer 103, for example, siliconoxide (SiO₂), is formed over the final layer. Any suitable method forforming or depositing the oxide layer that is known and available in theart can be used.

The transfer of the desired pattern into the desired layer utilizes twoseparate blocks formed into a common sacrificial layer 104. Therefore, afirst hardmask material 108 is deposited into the sacrificial layer.Suitable methods for depositing the first hardmask material include, butare not limited to, chemical vapor deposition and physical vapordeposition. Suitable materials for the first hardmask material includeinorganic hardmask materials, for example TiN, silicon nitride (SiN) andsilicon oxynitride (SiON). Preferably, the first hard mask material isTiN. To form the desired size and shape of the first block in twodimensions across the sacrificial layer, a first block mask 107, havingthe desired size and shape of the first block is placed on the firsthardmask material at the desired location of the first block. Suitablemethods for applying the first block mask include, but are not limitedto, ultraviolet resistivity and optical resistivity. The first blockmask includes an organic planarization layer (OPL) 105 in contact withthe first hardmask 108 and a silicon containing anti-reflective coating(SiARC) 106 located on top of the OPL such that the OPL is between theSiARC and the first hardmask material.

Referring now to FIG. 2, the shape defined by the first block mask isthen transferred or etched into the first hardmask material to createthe first block 110 in the sacrificial layer. Several steps are used toremove the first block mask and to etch the first hardmask material. Ina first step, the SiARC is removed using gas plasma etching such asreactive ion etching (RIE) with a gas that will etch or remove SiARC.Preferably, this gas is carbon tetraflouride (CF₄). In the second step,a gas plasma etching, e.g., RIE, is again used, however, with chlorinegas (Cl₂). This removes the first hardmask material that is not underthe OPL, etching the size and shape of the OPL into the first hardmaskmaterial. The OPL is then removed using any suitable process for etchingor removing an OPL that is known and available in the art. At thispoint, only the first block 110 remains in the sacrificial layer.

Having formed the first of the two separate blocks at the desiredlocation in the sacrificial layer, the second of the two separate blockscan be formed at another desired location in the common sacrificiallayer 104. Referring to FIG. 3, a second hardmask material 112 isdeposited into the sacrificial layer 104 and completely over and aroundthe first block 110 such that the thickness 113 of the second hardmaskmaterial is greater than the thickness 111 of the first block. Suitablemethods for depositing the second hardmask material include, but are notlimited to, chemical vapor deposition and physical vapor deposition.Suitable materials for the second hardmask material include inorganichardmask materials, for example TiN, silicon nitride (SiN) and siliconoxynitride (SiON). Preferably, the material of the second hard maskmaterial is SiN. Therefore, the first hard mask material is etched usinga first gas which does not etch the second hardmask material, and thesecond hardmask material is etched by a second gas that does not etchthe first hardmask material. This facilitates selective gas plasmaetching of the first and second hardmask materials. Referring to FIG. 4,the thickness of the second hardmask material is adjusted or decreasedto equal the thickness of the first block 110 and to expose a top 114 ofthe first block in the sacrificial layer. Suitable methods for adjustingthe thickness of the second hardmask material include, but are notlimited to, using RIE and a chemical-mechanical polish (CMP).

Referring to FIG. 5, to form the desired size and shape of the secondblock in two dimensions across the sacrificial layer, a second blockmask 115, having the desired size and shape of the second block isplaced on the second hardmask material 112 at the desired location ofthe second block. This location is separate and spaced from the locationof the first block 110 in the sacrificial layer. Suitable methods forapplying the second block mask include, but are not limited to,ultraviolet resistivity and optical resistivity. The second block maskincludes an OPL 117 in contact with the second hardmask material 112 anda SiARC 116 located on top of the OPL such that the OPL is between theSiARC and the second hardmask material.

Referring now to FIG. 6, the shape defined by the second block mask isthen transferred or etched into the second hardmask material to createthe second block 118 in the sacrificial layer without affecting thefirst block 110. Two steps are used to remove the second block mask andto etch the second hardmask material. In a first step, the SiARC isremoved and the second hardmask material is etched at the same timeusing gas plasma etching such as RIE with a gas that will etch or removeSiARC and the second hardmask material, e.g., fluoromethane gas (CH₃F).This removes the second hardmask material that is not under the OPL,etching the size and shape of the OPL into the second hardmask material.In the second step, the OPL is then removed using any suitable processfor etching or removing an OPL that is known and available in the art.Referring to FIG. 7, at this point, only the first block 110 and thesecond block 118 remain in the sacrificial layer. While the removal ofthe SiARC and the second hardmask material may result in some removal orgouging of the oxide layer 103, this layer is also a sacrificial layer,a slight gouging can be tolerated.

Referring now to FIG. 8, the complete sacrificial layer 104 isestablished by depositing a filling material 119 in the sacrificiallayer and over the first block 110 and second block 118. Suitablefilling materials are chosen to be selectively etched with either one ofthe first and second hardmask materials. In one embodiment, the fillingmaterial is a titanium containing anti-reflective coating (TiARC).Suitable methods for depositing the filling material include, but arenot limited to, chemical vapor deposition and physical vapor deposition.The filling material is deposited to this thickness 121 greater than athickness 122 of the first and second blocks. Referring to FIG. 9, thethickness of the filling material 119 is adjusted or decreased to equalthe thickness of the first block 110 and the second block 118 and toexpose a top 114 of the first block and a top 122 of the second block inthe sacrificial layer. Suitable methods for adjusting the thickness ofthe filling material include, but are not limited to, using RIE recessand CMP.

The resulting first and second block in the sacrificial layer are thenused in the transfer of a the critical dimensions of a desired patternto the final layer using a sidewall image transfer (SIT) process.Referring now to FIG. 10, an amorphous silicon layer 124 is depositedover the sacrificial layer 104, and another OPL layer 126 is depositedover the amorphous silicon layer. An organic anti-reflection coatinglayer 128 such as a silicon containing anti-reflective coating (SiARC)layer is deposited over the OPL layer. Any suitable methods known andavailable in the art form forming or depositing these layers includingCMP and physical vapor deposition. The plurality of resist mandrels 130are then formed and spaced on the top of the SiARC layer. One of theresist mandrels is located over the first block 110, and one of thespaces 132 between a pair of adjacent resist mandrels is located overthe second block 118.

Referring to FIG. 11, any conventional etching process is then used totransfer the pattern of resist mandrels 130 into the amorphous siliconlayer 124, resulting in a corresponding plurality of spaced amorphoussilicon mandrels 134. Again, one of the amorphous silicon mandrels islocated over the first block 110, and one of the spaces 135 between apair of adjacent amorphous silicon mandrels is located over the secondblock 118. Referring to FIG. 12, an oxide spacer layer 136 is depositedover the sacrificial layer and the plurality of amorphous siliconmandrels. Therefore, the top 138 and opposing sides 140 of eachamorphous silicon mandrel and the spaces 135 between and edges of thesacrificial layer 141 are covered by the oxide spacer layer. Suitableoxides and methods for depositing the oxide are known and available inthe art.

Referring to FIG. 13, the spacer oxide is then removed from the top 138of each amorphous silicon mandrel 134 and from portions of the space 135between each adjacent pair of amorphous silicon mandrels and portions ofthe edges of the sacrificial layer. This leaves a plurality of spacers142 extending up from the sacrificial layer on opposing sides 140 ofeach amorphous silicon mandrel. Each spacer is formed of the oxide usedfor the oxide spacer layer. The oxide spacer layer is etched using, forexample, an anisotropic etching process or RIE. The combination of eachamorphous silicon mandrel and spacers defines a mandrel criticaldimension 144, and the space between opposing pairs of amorphous siliconmandrels, which includes a spacer associated with each amorphous siliconmandrel, defines a non-mandrel critical dimension. The first block has afirst block width 148 that is equal to or greater than (and alignedwith) the mandrel critical dimension, and the second block has a secondblock width 150 that is equal to or greater than the non-mandrelcritical dimension.

The different materials of the first and second blocks are then utilizedin a separate gas plasma etching processes to transfer the criticaldimensions to the first and second blocks. Since gas etching can printsmaller dimensions, the use of a gas plasma etching process overcomesthe dimensional and functional limitations of other physical printingand etching processes in particular for 26 nm pitches and a 7 nm node.Referring to FIG. 14, RIE is used with Cl₂ gas to simultaneously etchthe TiARC 119 and the first block 110. This transfers the mandrelcritical dimension 144 to the first block. The second block 118 is notetched. But the TiARC is removed in the gaps 152 outside the spacers142, exposing the oxide layer 103. Referring to FIG. 15, all of thesegaps are filled with an additional OPL 154, using any suitable processof depositing an OPL into a plurality of gaps.

Referring now to FIG. 16, the amorphous silicon mandrels are pulled orremoved without affecting the first block 110 sized to the mandrelcritical dimension, the second block 118, the remaining portions of theTiARC 119 in the sacrificial layer, the additional OPL 154 and theplurality of spacers 142. In one embodiment, RIE with hydrogen bromidegas is used to remove the amorphous silicon mandrels. Referring to FIG.17, the non-mandrel critical dimension 146 is then transferred to thesecond block while simultaneously removing the TiARC 119 that is notmasked by the plurality of spacers 142. This results in a plurality ofTiARC spacers 156 corresponding in size and location to the oxide layerspacers 142. Again, a gas plasma etching process is used tosimultaneously etch the TiARC and the second block. In addition, theheight 158 will shrink, but the first block 110 will not be etched.Suitable methods for simultaneously etching the second block and theTiARC include using a gas plasma etching process such as RIE with CF₄.

Referring to FIG. 18, the additional OPL that were used a filler arethen removed, leaving the plurality of spacers 142 over the TiARCspacers, the first block 110 and the second block 118. Suitable methodsfor removing the additional OPL including using an OPL etching processas is known and available in the art. Referring to FIG. 9, the oxidespacers are removed and the pattern defined by the TiARC spacers 156,the first block 110 and the second block is simultaneously etched intothe oxide layer 103 below the sacrificial layer. Any convention oxideRIE process known and available in the art is used to remove the spacersand etch the oxide layer. This also exposes portions of the final layer,e.g., TiN or silicon, that are not masked or covered by the patterndefined by the TiARC spacers, the first block 110 and the second block118.

Referring to FIG. 20, these exposed portions can then be etched and theTiARC spacers, the first block and the second block simultaneouslyremoved using a suitable gas plasma etching process. In one embodiment,the gas plasma etching process is RIE with Cl₂ gas. Therefore, theremaining portions of the oxide layer can also be removed (not shown) byany suitable process, for example, oxide RIE. Overall, the desiredpattern containing the mandrel critical dimension, the non-mandrelcritical dimension and the oxide spacer dimensions is etched into thefinal layer. These dimensions are suitable for transistor patternshaving a pitch of 26 nm or less and a 7 nm node. The critical dimensionsare achieved with greater tolerances than possible with conventionaletching processes. Second and subsequent final layers can be added ontop of this final layer, and the desired patterns can be etched intothese second and subsequent final layers by repeating the blockformation and SIT process steps described above. Therefore, athree-dimensional pattern of transistors is formed in the semiconductordevice.

Referring to FIG. 21, exemplary embodiments are also directed to amethod for selective gas etching for self-aligned pattern transfer 200.A first block is formed in a sacrificial layer 202. The sacrificiallayer is a layer that is used to transfer the desired pattern to a finallayer, e.g., a TiN or silicon layer, in the semiconductor product. Thesacrificial layer can be located directly on top of the final layer oron top of an oxide layer that is on top of the final layer. The firstblock is formed of a first hardmask material that can be plasma etchedusing a first gas. Suitable first hardmask materials include inorganichardmask materials. In one embodiment, the first hardmask material isTiN, and the first gas is Cl₂. In one embodiment, the first block isformed by depositing the first hardmask material across the sacrificiallayer, and forming a first photoresist stack containing two layers, asilicon containing anti-reflective coating and an organic planarizationlayer, on the first hardmask material. The first photoresist stack has asize and location corresponding to the first block in the sacrificiallayer. Reactive ion etching with carbon tetrafluoride is used to removethe silicon containing anti-reflective coating. Next, reactive ionetching with the first gas, e.g., chlorine gas, is used to etch thefirst hardmask material that is not located under the first photoresiststack. Plasma etching, for example using any conventional plasma etchingtechnique, is used to remove the organic planarization layer, leavingonly the first block in the sacrificial layer.

A second block, separate from the first block is also formed in thesacrificial layer 204. The second block is formed from a second hardmaskmaterial that can be plasma etched using a second gas that is separatefrom the first gas. Suitable second hardmask materials include inorganichardmask materials. In one embodiment, the second hardmask material isSiN and the second gas is CH₃F. In one embodiment, forming the secondblock includes depositing the second hardmask material across thesacrificial layer and over the first block and adjusting a secondhardmask material thickness to equal a first block thickness. A secondphotoresist stack with two layers, a silicon containing anti-reflectivecoating and an organic planarization layer, is formed on the secondhardmask material. The second photoresist stack has a size and locationcorresponding to the second block. Reactive ion etching with the secondgas, e.g., fluoromethane, is used to remove the silicon containinganti-reflective coating and to etch the second hardmask material. Next,plasma etching, using any known plasma etching technique, is used toremove the organic planarization layer, leaving only the second blockand the first block in the sacrificial layer.

In order to provide for selective etching, the first and second hardmaskmaterials are selected such that the first hardmask material is notplasma etched using the second gas and the second hardmask material isnot plasma etched using the first gas. The first block and the secondblock are formed with dimensions along the sacrificial layer, i.e., intwo dimensions, that are greater than or equal to critical dimensions tobe transferred to layers below the sacrificial layer.

The first and second blocks in the sacrificial layer are then used in aselective gas etching process to transfer the desired pattern to thefinal layer 206. The gas etching provides for increased precision in thetransfer of critical dimensions and avoids pitch walking. In addition,the use of different gases allows for selective or targeted etching ofmaterials and masks at different steps in the process. In oneembodiment, the sacrificial layer with the first block and the secondblock is used in sidewall image transfer (SIT) to transfer the desiredpattern into layers below the sacrificial layer, i.e., the final layerand an oxide layer.

In order to using the first and second blocks to transfer the desiredpattern, a fill material is formed in the remaining portions of thesacrificial layer 208, i.e., portions that do not include the firstblock or the second block. In one embodiment, a fill material isselected that can be etched by both the first gas and the second gas. Inone embodiment, forming the fill material includes depositing a titaniumcontaining anti-reflective coating across the sacrificial layer and overthe first block and second block. The titanium containinganti-reflective coating thickness is then adjusted to equal a firstblock thickness and a second block thickness.

A plurality mandrels, preferably a plurality of amorphous siliconmandrels, are then formed on the sacrificial layer 210. The plurality ofmandrels is formed such that one mandrel is located above the firstblock and one space between adjacent mandrels is located above thesecond block. In one embodiment, forming the plurality of mandrels onthe sacrificial layer includes depositing an amorphous silicon layer onthe sacrificial layer, and depositing an organic planarization layer onthe amorphous silicon layer. A silicon containing anti-reflectivecoating layer is deposited on the organic planarization layer, and aplurality of resist mandrels is formed on the silicon containinganti-reflective coating layer. The amorphous silicon layer is etched toform the plurality of amorphous silicon mandrels corresponding to theplurality of resist mandrels. Any suitable methods known and availablein the art to deposit, form and etch these layers can be used. Byplacing the first clock below a mandrel and the second block below aspace between adjacent mandrels, the first block controls variations inthe width or size of mandrels, and the second block controls variationsin the width or size of the spaces between adjacent mandrels. Therefore,the first and second blocks are inversely controlling widths or criticaldimensions since increases in mandrel width will produce decreases inspace widths while decreases in mandrel width will produce increase inspace widths.

The first block, being located beneath a mandrel is used to transfer amandrel critical dimension to layers below the sacrificial layer 212,and the second block, being located beneath the spaced between adjacentmandrels is used to transfer a non-mandrel critical dimension to thelayers below the sacrificial layer 214. The lower layers include thefinal layer and the oxide layer. In one embodiment, an oxide spacer isdeposited over the plurality of amorphous silicon mandrels and thesacrificial layer. An anisotropic etching process is used to remove theoxide spacer from a top of each amorphous silicon spacer and from thespace between adjacent amorphous silicon mandrels. This leaves an oxidespacer, e.g., a vertical spacer, on either side of each amorphoussilicon mandrel. The first block extends completely under one of theamorphous silicon mandrels and the oxide spacers on either side of oneof the amorphous silicon mandrels. In addition, the second block extendscompletely under the one space between adjacent amorphous siliconmandrels and oxide spacers located on either side of the one spacebetween adjacent amorphous silicon spacers.

In this embodiment with the spacers located on either side of eachmandrel, first critical dimension is defined by and includes one of theamorphous silicon mandrels and the oxide spaces on either side of one ofthe amorphous silicon mandrels. The second critical dimension is definedby and includes the one space between adjacent amorphous siliconmandrels and the oxide spacers located on either side of the one spacebetween adjacent amorphous silicon mandrels. Since the first and secondblocks are formed of materials that are plasma etched using differentgases, the first gas and the second gas are used in separate reactiveion etching steps to transfer the first critical dimension to the firstblock and to transfer the second critical dimension to the second block.In one embodiment, the first gas is chlorine gas, and the second gas iscarbon tetraflouride gas.

In one embodiment, reactive ion etching with the first gas is used totransfer the first critical dimension to the first block, to transferthe first critical dimension into the titanium containinganti-reflective coating layer, i.e., the fill material, located underamorphous silicon mandrels and the oxide spaces on either side of theamorphous silicon mandrels and to remove the first block and titaniumcontaining anti-reflective coating layer located in spaces between oxidespacers located on either side of spaces between adjacent amorphoussilicon mandrels. Reactive ion etching with the second gas is then usedto transfer the second critical dimension to the second block and totransfer a spacer width for each oxide spacer to the titanium containinganti-reflective coating layer, i.e., the fill layer.

All spaces between oxide spacers located on either side of spacesbetween adjacent amorphous silicon mandrels are filled with a backfillorganic planarization layer following reactive ion etching with thefirst gas. Reactive ion etching with hydrogen bromide is used to removethe amorphous silicon mandrels before reactive ion etching with thesecond gas. Plasma etching is used to remove the backfill organicplanarization layer, and oxide reactive ion etching is used to removethe plurality of oxide spacers and to etch a final pattern into an oxidelayer below the sacrificial layer. The final pattern is defined by thesecond block, the first block and the spacer widths in the titaniumcontaining anti-reflective coating layer corresponding to each oxidespacer in the plurality of oxide spacers in the sacrificial layer.Reactive ion etching with ion gas is used to etch the final pattern intothe final layer, e.g., TiN, below the oxide layer and to remove thesacrificial layer. Therefore, the desired pattern is transferred intothe final layer.

In order to add additional two-dimensional patterns or to createthree-dimensional patterns in the multi-layer semiconductor produce, atermination is made regarding whether additional layers, and patterns inthose additional layers, are to be formed 216. If additional layers areto be formed, one or more additional final layers and one or moreadditional oxide layers are formed 218. Then the steps of forming thetwo blocks and using those blocks to transfer the desired criticaldimension are repeated. If not additional layers are needed, then theprocess is terminated.

As will be appreciated by one skilled in the art, aspects of the presentinvention may be embodied as a system, method or computer programproduct. Accordingly, aspects of the present invention may take the formof an entirely hardware embodiment or an embodiment combining softwareand hardware aspects that may all generally be referred to herein as a“circuit,” “module” or “system.” Furthermore, aspects of the presentinvention may take the form of a computer program product embodied inone or more computer readable medium(s) having computer readable programcode embodied thereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readable signalmedium or a computer readable storage medium. A computer readablestorage medium may be, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system,apparatus, or device, or any suitable combination of the foregoing. Morespecific examples (a non-exhaustive list) of the computer readablestorage medium would include the following: an electrical connectionhaving one or more wires, a portable computer diskette, a hard disk, arandom access memory (RAM), a read-only memory (ROM), an erasableprogrammable read-only memory (EPROM or Flash memory), an optical fiber,a portable compact disc read-only memory (CD-ROM), an optical storagedevice, a magnetic storage device, or any suitable combination of theforegoing. In the context of this document, a computer readable storagemedium may be any tangible medium that can contain, or store a programfor use by or in connection with an instruction execution system,apparatus, or device.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium may be any computer readable medium thatis not a computer readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wireline, optical fiber cable, RF, etc., or any suitable combination ofthe foregoing.

Computer program code for carrying out operations for aspects of thepresent invention may be written in any combination of one or moreprogramming languages, including an object oriented programming languagesuch as Java, Smalltalk, C++ or the like and conventional proceduralprogramming languages, such as the “C” programming language or similarprogramming languages. The program code may execute entirely on theuser's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on a remotecomputer or entirely on the remote computer or server. In the latterscenario, the remote computer may be connected to the user's computerthrough any type of network, including a local area network (LAN) or awide area network (WAN), or the connection may be made to an externalcomputer (for example, through the Internet using an Internet ServiceProvider).

Aspects of the present invention are described above with reference toapparatus (systems) and computer program products according toembodiments of the invention. It will be understood that eachdescription and illustration can be implemented by computer programinstructions. These computer program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the block diagram block orblocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the block diagram block orblocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the block diagram block orblocks.

The schematic illustrations and block diagrams in the Figures illustratethe architecture, functionality, and operation of possibleimplementations of systems, methods and computer program productsaccording to various embodiments of the present invention. In thisregard, each block in the block diagrams may represent a module,segment, or portion of code, which comprises one or more executableinstructions for implementing the specified logical function(s). Itshould also be noted that, in some alternative implementations, thefunctions noted in the block may occur out of the order noted in thefigures. For example, two blocks shown in succession may, in fact, beexecuted substantially concurrently, or the blocks may sometimes beexecuted in the reverse order, depending upon the functionalityinvolved. It will also be noted that each block of the block diagrams,and combinations of blocks in the block diagrams, can be implemented byspecial purpose hardware-based systems that perform the specifiedfunctions or acts, or combinations of special purpose hardware andcomputer instructions.

Methods and systems in accordance with exemplary embodiments of thepresent invention can take the form of an entirely hardware embodiment,an entirely software embodiment or an embodiment containing bothhardware and software elements. In a preferred embodiment, the inventionis implemented in software, which includes but is not limited tofirmware, resident software and microcode. In addition, exemplarymethods and systems can take the form of a computer program productaccessible from a computer-usable or computer-readable medium providingprogram code for use by or in connection with a computer, logicalprocessing unit or any instruction execution system. For the purposes ofthis description, a computer-usable or computer-readable medium can beany apparatus that can contain, store, communicate, propagate, ortransport the program for use by or in connection with the instructionexecution system, apparatus, or device. Suitable computer-usable orcomputer readable mediums include, but are not limited to, electronic,magnetic, optical, electromagnetic, infrared, or semiconductor systems(or apparatuses or devices) or propagation mediums. Examples of acomputer-readable medium include a semiconductor or solid state memory,magnetic tape, a removable computer diskette, a random access memory(RAM), a read-only memory (ROM), a rigid magnetic disk and an opticaldisk. Current examples of optical disks include compact disk-read onlymemory (CD-ROM), compact disk-read/write (CD-R/W) and DVD.

Suitable data processing systems for storing and/or executing programcode include, but are not limited to, at least one processor coupleddirectly or indirectly to memory elements through a system bus. Thememory elements include local memory employed during actual execution ofthe program code, bulk storage, and cache memories, which providetemporary storage of at least some program code in order to reduce thenumber of times code must be retrieved from bulk storage duringexecution. Input/output or I/O devices, including but not limited tokeyboards, displays and pointing devices, can be coupled to the systemeither directly or through intervening I/O controllers. Exemplaryembodiments of the methods and systems in accordance with the presentinvention also include network adapters coupled to the system to enablethe data processing system to become coupled to other data processingsystems or remote printers or storage devices through interveningprivate or public networks. Suitable currently available types ofnetwork adapters include, but are not limited to, modems, cable modems,DSL modems, Ethernet cards and combinations thereof.

In one embodiment, the present invention is directed to amachine-readable or computer-readable medium containing amachine-executable or computer-executable code that when read by amachine or computer causes the machine or computer to perform a methodfor selective gas etching for self-aligned pattern transfer inaccordance with exemplary embodiments of the present invention and tothe computer-executable code itself. The machine-readable orcomputer-readable code can be any type of code or language capable ofbeing read and executed by the machine or computer and can be expressedin any suitable language or syntax known and available in the artincluding machine languages, assembler languages, higher levellanguages, object oriented languages and scripting languages. Thecomputer-executable code can be stored on any suitable storage medium ordatabase, including databases disposed within, in communication with andaccessible by computer networks utilized by systems in accordance withthe present invention and can be executed on any suitable hardwareplatform as are known and available in the art including the controlsystems used to control the presentations of the present invention.

While it is apparent that the illustrative embodiments of the inventiondisclosed herein fulfill the objectives of the present invention, it isappreciated that numerous modifications and other embodiments may bedevised by those skilled in the art. Additionally, feature(s) and/orelement(s) from any embodiment may be used singly or in combination withother embodiment(s) and steps or elements from methods in accordancewith the present invention can be executed or performed in any suitableorder. Therefore, it will be understood that the appended claims areintended to cover all such modifications and embodiments, which wouldcome within the spirit and scope of the present invention.

What is claimed is:
 1. A method for selective gas etching forself-aligned pattern transfer, the method comprising: forming a firstblock in a common sacrificial layer, the first block comprising a firsthardmask material that can be plasma etched using a first gas; andforming a second block separate from the first block in the commonsacrificial layer, the second block comprising a second hardmaskmaterial that can be plasma etched using a second gas separate from thefirst gas; wherein the first hardmask material is not plasma etchedusing the second gas, the second hardmask material is not plasma etchedusing the first gas and the first hard mask and second hardmask coverdistinct locations within a given thickness of the common sacrificiallayer.
 2. The method of claim 1, wherein the first block and the secondblock comprise dimensions along the sacrificial layer greater than orequal to critical dimensions to be transferred to layers below thecommon sacrificial layer.
 3. The method of claim 1, wherein the firsthardmask material and the second hardmask material comprise inorganichardmask materials.
 4. The method of claim 1, wherein: the firsthardmask material comprises titanium nitride; and the second hardmaskmaterial comprises silicon nitride.
 5. The method of claim 1, whereinforming the first block comprises: depositing the first hardmaskmaterial across the common sacrificial layer; forming a firstphotoresist stack comprising a silicon containing anti-reflectivecoating and an organic planarization layer on the first hardmaskmaterial, the first photoresist stack having a size and locationcorresponding to the first block; using reactive ion etching with carbontetrafluoride to remove the silicon containing anti-reflective coating;using reactive ion etching with chlorine gas to etch the first hardmaskmaterial; and using plasma etching to remove the organic planarizationlayer, leaving only the first block in the common sacrificial layer. 6.The method of claim 5, wherein forming the second block comprises:depositing the second hardmask material across the common sacrificiallayer and over the first block; adjusting a second hardmask materialthickness to equal a first block thickness; forming a second photoresiststack comprising a silicon containing anti-reflective coating and anorganic planarization layer on the second hardmask material, the secondphotoresist stack having a size and location corresponding to the secondblock; using reactive ion etching with fluoromethane to remove thesilicon containing anti-reflective coating and to etch the secondhardmask material; and using plasma etching to remove the organicplanarization layer, leaving only the second block and the first blockin the common sacrificial layer.
 7. The method of claim 1, furthercomprising using the common sacrificial layer comprising the first blockand the second block in sidewall image transfer to transfer a desiredpattern into layers below the common sacrificial layer.
 8. The method ofclaim 7, wherein using the common sacrificial layer comprising the firstblock and the second block in sidewall image transfer further comprises:using the first block to transfer a mandrel critical dimension to layersbelow the common sacrificial layer; and using the second block totransfer a non-mandrel critical dimension to the layers below the commonsacrificial layer.
 9. The method of claim 1, further comprising:depositing titanium containing anti-reflective coating across the commonsacrificial layer and over the first block and second block; adjusting atitanium containing anti-reflective coating thickness to equal a firstblock thickness and a second block thickness.
 10. The method of claim 9,further comprising forming a plurality of amorphous silicon mandrels onthe common sacrificial layer such that one amorphous silicon mandrel islocated above the first block and one space between adjacent amorphoussilicon mandrels is located above the second block.
 11. The method ofclaim 10, wherein forming the plurality of amorphous silicon mandrels onthe common sacrificial layer comprises: depositing an amorphous siliconlayer on the common sacrificial layer; depositing an organicplanarization layer on the amorphous silicon layer; depositing a siliconcontaining anti-reflective coating layer on the organic planarizationlayer; forming a plurality of resist mandrels on the silicon containinganti-reflective coating layer; and etching the amorphous silicon layerto form the plurality of amorphous silicon mandrels corresponding to theplurality of resist mandrels.
 12. The method of claim 10, furthercomprising: depositing an oxide spacer over the plurality of amorphoussilicon mandrels and the common sacrificial layer; and using anisotropicetching to remove the oxide spacer from a top of each amorphous siliconspacer and from the space between adjacent amorphous silicon mandrels,leaving an oxide spacer on either side or each amorphous siliconmandrel.
 13. The method of claim 12, wherein: the first block extendscompletely under one of the amorphous silicon mandrels and the oxidespacers on either side of one of the amorphous silicon mandrels; and thesecond block extends completely under the one space between adjacentamorphous silicon mandrels and oxide spacers located on either side ofthe one space between adjacent amorphous silicon spacers.
 14. The methodof claim 13, further comprising using the first gas and the second gasin reactive ion etching to transfer a first critical dimension definedby one of the amorphous silicon mandrels and the oxide spaces on eitherside of one of the amorphous silicon mandrels to the first block and totransfer a second critical dimension defined by the one space betweenadjacent amorphous silicon mandrels and oxide spacers located on eitherside of the one space between adjacent amorphous silicon mandrels to thesecond block.
 15. The method of claim 14, wherein using the first gasand the second gas in reactive ion etching further comprises: usingreactive ion etching with the first gas to transfer the first criticaldimension to the first block, to transfer the first critical dimensioninto the titanium containing anti-reflective coating layer located underamorphous silicon mandrels and the oxide spaces on either side of theamorphous silicon mandrels and to remove the first block and titaniumcontaining anti-reflective coating layer located in spaces between oxidespacers located on either side of spaces between adjacent amorphoussilicon mandrels; and using reactive ion etching with the second gas totransfer the second critical dimension to the second block and totransfer a spacer width for each oxide spacer to the titanium containinganti-reflective coating layer.
 16. The method of claim 15, wherein thefirst gas comprises chlorine gas and the second gas comprises carbontetraflouride gas.
 17. The method of claim 15, further comprisingfilling all spaces between oxide spacers located on either side ofspaces between adjacent amorphous silicon mandrels with a backfillorganic planarization layer following reactive ion etching with thefirst gas; and using reactive ion etching with hydrogen bromide toremove the amorphous silicon mandrels before reactive ion etching withthe second gas.
 18. The method of claim 17, further comprising: usingplasma etching to remove the backfill organic planarization layer; andusing oxide reactive ion etching to remove the plurality of oxidespacers and to etch a final pattern into an oxide layer below the commonsacrificial layer, the final pattern defined by the second block, thefirst block and the spacers widths in the titanium containinganti-reflective coating layer corresponding to each oxide spacer in theplurality of oxide spacers in the common sacrificial layer.
 19. Themethod of claim 18, further comprising using reactive ion etching withion gas to etch the final pattern into a final layer below the oxidelayer and to remove the common sacrificial layer.
 20. The method ofclaim 19, wherein the final layer comprises titanium nitride.